Glycosides

Widely distributed in plants, glycosides comprise a large group of secondary metabolites. Gycosides are structurally diverse and given their proven bioactivities and traditional use, they are of great importance to the regime of pharmacognosy; still there remains much to be elucidated on their roles and properties. Similar to all glycosides is a construction consisting of two parts, an aglycone (genin) unit, which is mainly lipophilic, and a glycone unit which is hydrophilic and composed of one or more sugar components. In this chapter, natural plant glycosides, such as phenolic and flavonoids, coumarins, chromones, anthraquinones, saponosides, cardiac, cyanogenic, and thioglycosides have been characterized; their chemistry and structure–activity relationships, plant sources, and extraction methods are also discussed. Further, the chapter reflects the traditional and well-documented therapeutic uses, mechanisms of action, possible adverse effects and toxicity of these metabolites, and also the prospects and trends in evaluating natural glycosides as new effective therapeutics.